Too many issues but let me name some(maybe spoilers)
1.After 2 seasons everyone is still fresh and clean try find dirt on anyone it's impossible.
2.They guys weed vape's batteries are infinite lasting a season and a half
3.Levi is in the military yet he brings a pistol with no extra ammo,
4. They had 3 guns and they all magically disappeared
5. The CGI is horrible, the Saber tooth tiger runs like a wounded hippo
6. Why didn't they put 1 bullet in the sloths head that ate all there food they could have made sloth jerky that would last years
7. Levi attacks the guards by the mine twice why is he still alive
8. The wolf's of 10000 bc apparently would attack large groups of creatures the same size as them instead of the typical weakest one that wonders off
9.When there is fog the wolf's loose there smell and become deaf as well
Too much wrong with this series but I will say it had a good concept and potential I didn't hate it, but the director and producer thinks his audience are really stupid or he got very lazy and some of the things you just can't ignore